(1) Field of the Invention
This invention relates to a tool for working on sucker rods, and more particularly to a gripping socket for an impact wrench to remove couplings from sucker rods and also a socket to attach and remove protectors for sucker rod pins. An oil field worker who works on sucker rods is one having ordinary skill in this art.
(2) Description of the Related Art
Sucker rods for oil wells are threaded on both ends, or stated in common terminology, they have pins on both ends. The pin includes a radial shoulder or flange which is a friction surface upon which the couplings are torqued. Inboard of the flange having the shoulder, are wrench flats, i.e., the rod at that point has a square cross section. Normally a nonadjustable wrench which has one open side is used to grasp the wrench flat.
The sucker rods are connected by couplings. The coupling is a short threaded tube which is threaded onto the pins. In many cases, a sucker rod string will be over 5,000 feet in length, and normally, they are made of steel. Therefore, it may be seen that there is considerable weight upon the sucker rod. In addition to weight, there is stress reversal in use, reversing the stress with every stroke of the pump. For this reason, the American Petroleum Institute (API) has adopted specifications and standards for the sucker rods, couplings, threads, and also, the torque of the coupling attached to the pin. All of this is critical so that the couplings will not break or loosen during use.
Often the rod string is subject to severe corrosion. Often the couplings will have special coatings on them to prevent corrosion. It is necessary that this coating not be ruptured or badly indented because the resulting strain upon the coupling will enhance corrosion. After use, the couplings often bond to the rods upon which they are attached.
The sucker rod string connects a pump jack upon the surface of the earth to a pump far beneath the surface. Since the pump is subject to corrosion, erosion, and wear, it is necessary to pull the pump for maintenance and repair. Pulling the pump entails pulling the sucker rod from the well. Normally sucker rod joints are 25' in length. Normally the sucker rod will be pulled from the well in stands; a stand being three sucker rods. With the 25' sucker rods in a 5,000' well, it is seen that there would be 200 sucker rods within the well. Any time a well is pulled, it is not unusual for 10%-20% of the couplings to be replaced because of wear or corrosion damage. In some instances, all of the couplings will be replaced. In many instances, all of the couplings will be removed from the rods and the pins inspected for corrosion and other damage.
Often, the crew either pulling the rods from the well or running the rods back in the well will be furnished with power tongs. Power tongs in the tool which fits upon the wrench flats to torque the sucker rods when they are being run into the well or which break the joint of the sucker rod to the coupling when they are coming out of the well. Except for inspection or replacement, the coupling will be left upon one of the pins of the sucker rod.
Obviously, for a complete inspection or replacement, it is necessary that a coupling be removed from the sucker rod after the joint of sucker rod has been separated from the string.
Before this invention, it was commercial practice to remove the coupling from the sucker rod using hand tools.
Often for complete inspection and renovation of the pins of a sucker rod, the sucker rod is transported to a shop. After the pins have been cleaned, inspected, and lubricated, a thread protector is placed over the thread. The thread protector is normally a synthetic material, elastomer, which is normally attached to the pins by driving it on with a hammer. The exterior of the protector is fustroconic with 16 splines thereon.
With protectors driven on by hammer, some are very securely attached. However, some protectors are not securely attached and will drop off in transportation and handling. Also, the protectors that are securely attached are difficult to remove and are often removed by using a screw driver as a chisel to pry them off. The thread protectors may be screwed upon the pins; however, with the present shape of the protectors and the tools available, this is impractical to either screw them on or screw them off.